Naturally occurring crude oils and other fossil fuels may contain a small amount of mercury depending on the location of their production. Mercury, as an impurity in fuels, is a potential cause of such problems as catalyst poisoning and damage to facilities used in refining, reforming or petrochemical processes. Natural gas and the oils that accompany their production often contain mercury. Several technologies for removing mercury from hydrocarbon gases have been practiced at many commercial NG plants. However, no commercial method for successfully removing mercury from hydrocarbon oils(hydrocarbon liquids) and other oils that are produced in conjunction with the production of natural gas has yet been developed.
The present invention relates to a technology for removing mercury from such hydrocarbon oils. More particularly, the present invention relates to a method for removing mercury selectively and efficiently by utilizing the mechanism of contact with a copper compound and/or a tin compound.
Techniques for removing mercury present as a trace impurity in other substances have been described in numerous reports. In one method, mercury in waste water is removed with the aid of a chelating agent, sulfur, activated carbon, an ion-exchange resin, etc. In another method mercury in waste gases such as combustion gases and air are removed using a molecular sieve, lead sulfide, an alkaline reducing agent, a chelator-supporting activated carbon or an aqueous solution of permanganate. These and other methods known in the art of mercury removal are mostly intended for use in environmental pollution control.
Techniques are also available to remove mercury from natural gas using zeolite or a sulfur-supporting (sulfur-implegnated) activated carbon. However, their availability is limited to hydrocarbons in gaseous form.
As will be understood from the above, disclosures of prior art methods of removing trace mercury from fluids are very scarce. Methods are known for removing trace mercury from vacuum pump oils which comprises using zinc sulfide. However the percentage of mercury that can be removed from hydrocarbon oils by adopting these methods, for all practical purposes is far from being satisfactory. Therefore, a strong need exists for developing a method that is capable of the selective and efficient removal of mercury from hydrocarbon oils.